In order to satisfy a wireless data traffic demand that tends to increases after the 4th generation (4G) communication system commercialization, efforts to develop an improved 5 (5G) communication system or pre-5G communication system is being made. For this reason, the 5G communication system or pre-5G communication system is called a beyond 4G network communication system or a post LTE system.
In order to achieve a high data transfer rate, the 5G communication system is considered to be implemented in a mmWave band (e.g., 60 GHz band). In order to reduce a loss of electric waves and increase the transfer distance of electric waves in the mmWave band, beamforming, massive MIMO, full dimensional MIMO (FD-MIMO), array antenna, analog beam-forming and large scale antenna technologies are being discussed in the 5G communication system.
Furthermore, in order to improve the network of a system, technologies, such as an improved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, device to device communication (D2D), wireless backhaul, a moving network, cooperative communication, coordinated multi-points (CoMP) and reception interference cancellation, are being developed in the 5G communication system.
In addition, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) that are advanced coding modulation (ACM) schemes, improved filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) are being developed in the 5G system.
As described above, if the massive MIMO antenna system is adopted, there is a need for a technology for previously obtaining phase information between antennas and performing phase alignment between the antennas. A technology using phase alignment as described above is called an antenna calibration technology. The antenna calibration technology is chiefly used when beam-forming (BF) is chiefly used. For antenna calibration, there is a need for a process of estimating phase information on each antenna by transmitting a given calibration signal.
The massive MIMO system is a system for increasing the signal to noise ratio (SNR) of transmitted and received signals using massive antennas in order to improve data transmission efficiency. In LTE release 13/14, the massive MIMO system has been standardized as full-dimension multiple-input multiple-output (hereinafter FD-MIMO) and is also discussed as a major component technology even in the 5G communication system.
In the massive MIMO system, if antenna calibration is performed, the time taken for the antenna calibration increases because calibration must be performed on a large number of antennas. Furthermore, this acts as a burden of a system in that antenna calibration must be performed in the state in which typical communication services are stopped while the antenna calibration is performed. Particularly, in the massive MIMO system, the time taken for antenna calibration is further increased because the antenna calibration must be performed on each of a large number of antennas that much. As described above, a lot of time taken for antenna calibration may be a great burden on a system because the time during which communication is stopped is increased.
Accordingly, there is a need for an apparatus and method for reducing the time taken for antenna calibration in the massive MIMO system.